1. Field of the Invention
The present invention relates to a lower-limb joint orthosis suitable for use by a paralyzed person whose lower-limb, particularly foot region, is paralyzed, and also relates to a control method therefor.
2. Description of the Related Art
The forms of paralysis of the foot region include: hemiplegia in which mainly one foot is paralyzed due, for example, to apoplexy; and paraplegia in which, in many cases, both feet are paralyzed due, for example, to a spinal cord injury. In either case, it is often difficult or impossible to walk independently. Accordingly, when a person with such a paralysis walks, they need some aid. A conventional aid of this type fixes from the lower leg to the foot by a splint-like object.
This makes it possible to stabilize an upright position, or prevent the person from, for example, stumbling due to the lowering of the toe when separating the foot region from the ground to take a step. A joint function, however, is not provided, and therefore, it is not possible to bend and stretch the ankle in accordance with the shift of the center of the body weight, or absorb shock when the sole makes contact with the ground. Accordingly, walking with the aid attached places a large burden on the body. This causes a paralyzed person to avoid walking independently with the aid attached, or walking with minor assistance. Consequently, also the walking function fails to be improved.
It should be noted that Patent Literature 1 (Japanese Laid-Open Patent Publication No. 2001-299790) shows a lower-limb joint orthosis incorporating a hinge mechanism in the portion corresponding to the ankle joint. In this prior example, however, the orthosis for assisting independence is merely provided with a rotational movement function, and the range of rotational movement is limited to a very narrow range, which does not correspond to a wide angle from landing to stepping. Further, although the locking and unlocking of a hinge mechanism is incorporated, the operation of the hinge mechanism requires the operation of a locking member, which is complicated and cumbersome.
In response, the present applicant has proposed, as the following Patent Literature 2 (Japanese Laid-Open Patent Publication No. 2006-087559), a technique of: providing, in the portion corresponding to the ankle joint, a rotary cylinder in which an MR fluid whose viscosity changes depending on a magnetic force is enclosed; coupling a rotor and a stator of the rotary cylinder to an upper component to be attached to the lower-limb, and to a lower component that supports the foot region; adjusting the viscosity of the MR fluid by adjusting the magnetic force in accordance with the shift of the body weight borne by the sole during walking; and switching the bending and stretching of the ankle (the upward and downward rotational movement of the foot region relative to the ankle) from a disabled or semi-disabled state (referred to as a “locked state”) to a freely moving state (referred to as a “free state”). This technique, however, tends to complicate the structure of the lower-limb joint orthosis, and increase the size of the lower-limb joint orthosis.